Such electromagnetic actuators, in technical terminology also called proportional magnets or switching magnets, are freely available on the market in a variety of embodiments. An actuator provided in particular for actuating a valve of this type is described for example in DE 10 2008 061 414 A1. In such devices, the armature performs a stroke movement in the pole tube upon electrical energization of the associated coil winding. Upon de-energization of the coil winding, as a rule, the armature is returned to its home position by a restoring force. In most cases, the restoring force acts on the armature via an armature-connected actuator member, which is designed, for instance, rod-shaped, extends through the pole core and triggers a relevant actuation procedure, for instance, in an externally connected valve for controlling fluid flows. Depending on the application, a specific determined response behavior of the actuating device is required. More specifically, a certain course of the magnetic force-displacement curve is required for associated switching and control functions. The geometry of the pole tube in the transition region between the magnetic separation area and the pole core is particularly decisive for the course of this F-d curve. The manufacturer of such actuation devices then has to manufacture and offer different pole core systems, as needed, i.e. depending on whether a customer wants a rising characteristic, an approximately horizontal characteristic, or a falling characteristic. In particular for small quantities, customization to customer wishes leads to increased manufacturing costs.